Various ophthalmic and medical applications require a hand-held dispenser of multiple doses of sterile liquids. Sterile saline is required by contact lens wearers for use as a rinse solution, for rinsing the lens prior to inserting the lens in the eye, and also for soaking the lens during the cleaning and disinfecting process. Dispensers have been designed to maintain such liquids in a sterile state for dispensing, such as disclosed in the present inventor's U.S. Pat. No. 5,507,417, which discloses a dispenser for sterile saline solution and U.S. Pat. No. 6,745,763 which discloses a vaporizing device for administering sterile medication. Similarly, dispensers of medicinal liquids for eye, ear and nose drops desirably keep such liquids sterile between uses to prevent bacterial growth. An example of such device is disclosed in U.S. Pat. No. 4,533,068 Meierhoefer, wherein a hydrophobic filter is used to sterilize the replacement air which enters the dispenser upon release of the squeezing pressure. Other devices use an anti-bacterial hydrophobic filter over the outlet port, or hydrophobic and hydrophilic filters in tandem, to maintain the liquid sterile. See U.S. Pat. No. 3,149,758 Bush et al.; U.S. Pat. No. 4,938,389 Rossi et al. and Kramer et al. U.S. Pat. No. 4,463,880.
Commonly such dispensers use a one-way valve or pump with a one-way valve to dispense the sterile liquid from a squeeze bottle or collapsible reservoir. A problem with existing devices is that after the sterile liquid is dispensed, some residue remains on the outlet port, or is drawn back into the outlet conduit, which can become contaminated with bacteria or the like and which will contaminate the next dose of the sterile liquid which is dispensed through the outlet port. There is therefore a need to avoid the foregoing problem with sterile liquid dispensers.